People's habits concerning consumption of video content (titles, e.g., movies, television programs, episodes, etc.) have been changing for some time. Traditionally, linear (regular) channels containing video content were and still are broadcasted (usually by Pay-TV operators) over satellites and over cables to many millions of end users, wherein to watch a certain title an end-user has to watch the title at the time it is transmitted (or record the content at the time it is transmitted e.g., for subsequent viewing). In recent years, linear television service providers (Pay-TV operators) have been responding to a trend led by the young generations and have been offering Video on Demand (VOD) services, which allow end users to watch content of their choice (out of libraries containing thousands of titles) at times of their choosing. In addition, with broadband Internet services becoming widely available and affordable, VOD services are also provided over the Internet by Internet VOD service providers (sometimes also referred to as Over the Top (OTT) VOD providers). Satellite Pay-TV operators (also referred to as Direct to Home (DTH) services) use hybrid set-top-boxes (STBs). These STBs allow DTH users to watch linear television channels (broadcasted over a satellite), access a relatively small selection of titles stored in their STBs (broadcasted over the satellite (Push VOD)), and to download titles over terrestrial broadband Internet links (IP VOD or OTT VOD).
Known technologies for delivering Video on Demand (VOD) services can be classified into three major classes:
(1) Near VOD: In order to allow an end user to watch a title at almost any time of his or her choosing (also sometimes referred to as Pay per View (PPV)), the service provider continuously broadcasts multiple copies of the title with short time offsets between the copies (typically 10-20 minutes, depending on the overall length of the title). That way, the end user needs to wait only a few minutes until they can get content of their choosing. Even though a short delay could be experienced until the content of choice is delivered, many would still consider such a service convenient. Technologies of this type are often limited to providing access to a relatively small number of titles, mainly due to their utilizing substantial bandwidth. These technologies do, however, still utilize far less bandwidth than needed for an on demand service.(2) Push VOD: The technologies in this category make use of a personal video recorder (PVR), usually installed at the end user's premises, for storing selected content. The selected content (usually content which is likely to be of interest to many end users) is often broadcast either overnight using spare capacity (or at other times when the media is not entirely utilized for other services) or all day long but at a low rate (to consume relatively little capacity or bandwidth). While such technologies are quite efficient in terms of bandwidth, to provide good user experience the service provider needs to push and store large volumes of content (hundreds of Gigabytes to several Terabytes) to the end user's PVRs. To store such high volumes of content, the PVRs need to be equipped with storage means suitable for storing very high volumes, which could make such PVRs relatively expensive.(3) On Demand: Each end user has a set-top-box (STB) that usually receives broadcasts of linear channels and streams the selected channel to the end user's screen. When content is requested on demand, the STB establishes a unicast session with the VOD provider's server (usually over a broadband Internet link), downloads the requested content from the VOD provider's server, stores it in local storage and then streams it to the end user's screen. Since each transmission is received by a single end user (e.g., due to the content being transmitted using a unicast service), the number of times a title is transmitted equals the number of times it is requested, i.e., the more users there are, the more bandwidth they consume. Thus, the main problem with these types of technologies is that they utilize huge amounts of capacity (e.g., bandwidth). In 2013, VOD services Netflix (https://www.netflix.com/) and YouTube (http://www.youtube.com/) generated half the overall peak-hour Internet traffic in the U.S. Netflix subscribers alone were responsible for about one third of the overall peak-hour Internet traffic in the U.S., generating some 7 million sessions.